Austin police on Sunday called on whoever is responsible for the recent string of deadly package bombings at East Austin homes to come forward and share their “message.”

“These events in Austin have garnered worldwide attention, and we assure you that we are listening,” interim Police Chief Brian Manley said at a news conference. “We want to understand what brought you to this point, and we want to listen to you.”

He pleaded with community members to share information that could lead to an arrest, and he said $50,000 has been added to the pot of money available in exchange for information about the attacks, which killed two people and seriously injured an elderly woman.“We don’t know what the ideology is behind this or what the motive is behind this,” he said.

Manley said more than 500 federal agents are assisting the Police Department in the investigation, including officials from the FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives. Authorities have followed up on 435 leads that led to 236 interviews, the Austin American-Statesman reports.

The fourth bombing was reportedly triggered by a trip wire , and it seriously injured two men walking on a sidewalk.

In the television interview Monday, Manley also addressed speculation that the bombings, which killed two African-Americans in neighborhoods east of Interstate 35, could be a hate crime.

“The victims in this incident were two Anglo males,” the chief said. “We’ve said from the beginning that we're not willing to rule anything out, just because when you rule something out you limit your focus.”